Optically active 2,2-dimethylcyclopropanecarboxylic acid, especially its optically active substance (S-isomer or the like) is a compound which is quite useful as an intermediate of agricultural chemicals such as an insecticide (refer to a specification of British Patent No. 1,260,847) or medications (refer to Kagaku to Seibutsu (Chemistry and Biology), 19, 204 (1981), EP 0,048,301 and the like). Especially, the S-isomer ((S)-(+)-2,2-dimethylcyclopropanecarboxylic acid) is a compound represented by the following formula (2), and this is an optically active substance which is more useful as a production intermediate.

With respect to a method for optical resolution of optically active 2,2-dimethylcyclopropanecarboxylic acid, there have been to date several reports. For example, a method for optical resolution by crystallization after derivatization into a diastereomer ester with a chiral alcohol or a diastereomer salt with a chiral amine (refer to a specification of British Patent No. 1,260,847, JP-A-60-25956, JP-A-60-56936 and the like) is known. For the diastereomer method, the improvement in optical purity or yield has been required in comparison to an asymmetric synthesis method.
For example, according to a method for optical resolution with phenylethylamine, a yield and an optical purity are both insufficient. According to a method using an ester with 1-menthol (refer to JP-A-60-25956), a satisfactory optical purity is provided, but the method is relatively troublesome because derivatization into an acid chloride or the like is conducted.
Assuming that a desired optical purity is attained by the optical resolution method, an optical resolution agent is expensive. Accordingly, when production was estimated on a large scale, there was a problem that recovery of the optical resolution agent had to be taken into consideration.
Under these circumstances, further improvements have been required for the optical resolution or optical purification method.